The relationship between step variability, muscle strength and functional walking performance in children with post-traumatic brain injury.

The objective of this study was to investigate the association between step variability, muscle strength and functional walking performance in children post-traumatic brain injury (TBI) and typically developed (TD) children. A convenience sample of 16 children post-TBI and 16 TD age and sex matched controls participated in this cross sectional study. The main outcome measures included step length and step time variability, measured with an electronic walkway, strength of four lower-extremity muscle groups, tested bilaterally with a hand held dynamometer, walking performance as assessed by the 2-min walk test, energy expenditure index (EEI) and rating of perceived exertion (OMNI scale). Significant differences were found in walking parameters between the groups (e.g., 2-min walk test: TBI 109+/-31 compared to TD 168+/-19 m). Children post-TBI had significantly greater variability in step time and step length in comparison to TD controls (e.g., step length variability: TBI 16.3+/-13.6 compared to TD 4.9+/-2.0). TD children had significantly higher mean strength values than children post-TBI in the knee extensor and hip abductor muscle groups (p<0.05). The 2-min walk test correlated inversely with the step time and length variability only among children post-TBI while muscle strength values correlated positively with the 2-min walk test only in TD children. This study found that step time and length variability and lower-extremity muscle strength correlated differently to distance covered during the 2-min walk test among children post-TBI and among TD children.